At least since WWII, light aircraft (General Aviation and, more recently, unmanned aircraft (UAVs)) have been powered by an aircooled, gasoline fueled engine that was typically formed in an opposed six cylinder arrangement. Such engines were fueled by very high octane AvGas. Problematically, the non availability of AvGas in the remote portions of the world has meant that general aviation was largely unavailable in such areas, the very areas of the world that need general aviation services the most. More recently it has been seen that refineries have been reluctant to produce AvGas, thereby stretching the world's supply. While all fuels are not cheap, AvGas has been especially costly.
In contrast to the relative scarcity and costliness of AvGas, relatively inexpensive diesel fuel and/or jet fuel (JP) is much more generally available throughout the world. While the quality of such fuel can vary greatly from place to place, a compression combustion engine can burn either diesel fuel or jet fuel (JP) about equally as well. The variances can be recognized as variance in the Cetane number (CN) of the fuel, a knowable characteristic of the fuel.
However, such a compression combustion engine presents a number of challenges to its designer, including:
a torque signature friendly for propeller harmonics;
fuel systems redundancy;
turbocharging design;
Bank-Bank main bearing loading; and
descent power requirements.
There is a need worldwide for an aero engine that can operate on such fuel (diesel fuel or jet fuel (JP)), yet accounts for the challenges noted above.